Oscilloscope power supply circuit
The power supply circuit supplies the negative high voltage and filament voltage required by the vertical and horizontal amplification circuits, scanning and synchronization circuits, and oscilloscope tubes and control circuits.
It can be seen from the functional block diagram of the oscilloscope that the measured signal voltage is added to the Y-axis input end of the oscilloscope, and is added to the vertical deflection plate of the oscilloscope tube through the vertical amplification circuit. Although the horizontal deflection voltage of the oscilloscope uses sawtooth voltage in most cases (for observing waveforms), other applied voltages are sometimes used (for measuring frequency, phase difference, etc.), so at the input end of the horizontal amplification circuit There is a horizontal signal selection switch to select the sawtooth wave voltage inside the oscilloscope as needed, or to use other voltages applied to the X-axis input end as the horizontal deflection voltage.
In addition, in order to keep the graphics displayed on the fluorescent screen stable, the frequency of the sawtooth voltage signal and the frequency of the measured signal are required to be synchronized. In this way, not only the frequency of the sawtooth wave voltage is required to be continuously adjusted, but also a synchronization signal must be input to the circuit that generates the sawtooth wave. In this way, for a simple oscilloscope (such as the domestic SB10 oscilloscope) that can only generate one state of continuous scanning (that is, generating a recurring and continuous sawtooth wave), it is necessary to input a frequency related to the frequency of the observed signal on its scanning circuit. Synchronization signal to contain the oscillation frequency of the sawtooth wave. For oscilloscopes with a waiting scan function (that is, no sawtooth wave is generated at ordinary times, and a sawtooth wave is generated when the measured signal arrives, and a scan is performed) (such as the domestic ST-16 oscilloscope, SR-8 dual-trace oscilloscope, etc. Specifically, it is necessary to input a trigger signal related to the signal under test on its scanning circuit, so that the scanning process closely cooperates with the signal under test. In order to adapt to various needs, the synchronization (or trigger) signal can be passed through the synchronization or trigger signal selection switch To choose, there are usually three sources: ① The measured signal is introduced from the vertical amplification circuit as a synchronization (or trigger) signal. This signal is called an "internal synchronization" (or "internal trigger") signal; ② Introducing some kind of related The external signal is a synchronization (or trigger) signal, which is called an "external synchronization" (or "external trigger") signal. This signal is added to the external synchronization (or external trigger) input terminal; ③ Some oscilloscopes also have a synchronization signal selection switch. The "power synchronization" gear is a 220V, 50Hz power supply voltage that is stepped down through the secondary of the transformer as a synchronization signal.
